An update on taking toepad pictures

This is an update from my previous blog post on Toepad pictures. 

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I’ve taken more than four hundred toepad pictures using the new macro photography technique I introduced  in an earlier post and I’ve learned a few tricks that I want to share in this update.

First and foremost, I highly recommend this approach. For those of you looking to capture a lot of toepad data, particularly in the field, this kit is way faster and more portable than using a flatbed scanner and the images I’m getting are at least as sharp.

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A few tips:

  • Petri dishes work great as a clear platform to place the lizard feet on. I found that the 60 mm diameter dishes were much easier to balance atop the lens (~40 mm in diameter) than the larger dishes I’d originally shown.
  • I cut and taped a scale bar to one edge of the petri dish so I wouldn’t have to worry about juggling a lizard and a tape measure.
  • Make sure you have several petri dishes – they scratch fast – and keep some ethanol and a kimwipe close at hand.

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  • The app that lets you remotely trigger your iPhone is absolutely maddening. Do not download it. I’m not even going to relink the name. Instead, I suggest a much more stable alternative: connect your phone to your computer with the USB cable, open QuickTime Player, select File > New Movie Recording and click the down arrow next to the record button. This will give you the option to select your attached iPhone as a recording device. This live-view is far more stable and less frustrating. *Windows and android users I’m afraid I haven’t had an opportunity to sort out a solution for those platforms. If you know of something that works, please include in the comments!

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Unfortunately, through the live view all you can see is whether the lizard is in position. You cannot remotely trigger the shutter this way. That means you’ll need a second pair of hands to help. I found it worked best when my partner was in charge of putting the ID tag in the frame after I’d placed the lizard foot and then pushing the volume button on the side of the phone to trigger the camera shutter.

  • Lighting is really important. I suggested a headlamp in the previous post providing an oblique light source through the diffuser around the lens. I tried using a microscope fiber optic light source but I was really unhappy with the “warmth” of the light. I found that the white-LEDs in my headlamp produced a much more realistic looking image (see above). Also, make sure you don’t have any light sources above/behind the subject. Backlighting confuses the camera’s auto-contrasting and results in dark and sometimes unfocused images.

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A new method for taking toepad pictures in the field!

This is a reblog of a post I wrote over on Anole Annals

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Getting good pictures of lizard toepads in the field can be tricky. Flatbed scanners are heavy and don’t take well to transit bumps and bruises, and getting a digital camera to focus on the toe, not the glass, requires surgical precision on the manual focus ring. I’ve just found a new solution for an iPhone (or GooglePixel, if that’s how you roll), and I’m eager to share.

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Drones to data

I’ve posted a lot of really pretty drone pictures and video these last six months and I’m realizing that this drone is actually pretty exciting tool for science communication. A reporter the other day said that she’d watched my Redonda video as part of her background research and it really helped her get a feel for the island. The original intent for the drone though was to capture high-resolution aerial photos of study sites to try to capture data on important but hard to measure ecological characteristics like vegetation cover, habitat availability, and maybe even habitat structure.

It’s a rainy Saturday in Boston so I decided to go back and look at some pictures from sunny Greece and see if I could start working with the drone footage to get some data.

The first step is actually capturing the video, of course, and that happened in Greece. I flew at a constant height (40m) in a straight line along the long axis of the island with the drone camera pointing 90 degrees straight down.

Here’s what that video looks like (don’t forget to click HD):

Now, that’s really pretty but for analyses I want a single, static image of the whole island. One option would be to just fly really high so the entire island is in the field of view. Unfortunately, since this island is so long, that’d have put me way higher than I wanted (or was allowed) to fly. This would also cause the resolution to suffer – I want to be able to see individual plants pretty clearly. The other option is to decompose that video, frame by frame, into a series of still images that I can then stitch together into a panorama.

This is actually pretty straight forward in in photoshop:

File > Import > Video Frames to Layers…

In this dialog box you select the video you want to make into still images and how many frames you want to skip per layer (the default is one layer every 2 frames). I chose one layer per 30 frames or approximately 1 image per second of video. That’ll give me good overlap to stitch the panorama together but not so many images that my poor computer will have to jigsaw hundreds of pictures together. You can then save those layers as independent images.

The final step then is just stitching together the panorama! Again in photoshop:

File > Automate > Photomerge…

Default settings worked great for me and voila, a beautiful high-resolution aerial photograph of an island in Greece.

Agios Artemios

Click on the image for a high-res look at Agios Artemios

So what about the data? I used my Oru Kayak seat as a launching pad on each of these islands. You can see it as the bright orange oval in the bottom third of the island. That orange launch pad is 80 cm across. With that I can set a scale that’s consistent for the whole island. I also know that the kayak is 360 cm long, which means I can check my calibration to make sure I’m getting good estimates. After that, it’s time to measure. I’m running out of time today so I haven’t made measurements but I’ll be calculating the  area of the island, the area of the green space, maybe even some metrics of patchiness, stay tuned!

Catching Anoles

As I alluded to in a previous post, we had to catch a lot of lizards from these sites! We needed at least 80 A. sagrei from Andros and we were also on the lookout for any other anole species we could find.

Much like my lizards in Greece, we used long fishing poles with a little loop at the end to slip around the lizard and grab them. Here’s a video demonstrating the process from Greece:

Very different however was that these anoles are quite a bit smaller than my wall lizards. Many of them weigh less than half a decent-sized Podarcis from Naxos. That meant that the nooses had to be tied with light dental floss, and the catching was a little less forgiving. If the noose was too “stiff” then the lizards would just dash right through the hole before the string could close around them.

There was one positive however: if you spook a Podarcis they often dash off and it’ll be a few minutes before you see them again for a second try. With these anoles if I startled them with a missed catch they’d often run four inches to the side and then stare up at you, allowing a second chance. And a third, and a fourth, and a fifth. Too often it came to that, they can be a bit squirrel-y around tree trunks and in the undergrowth.

One missed catch however particularly stands out in my memory – it was a first of its kind for me. I was nicely lined up for a grab of a nice sagrei when all of a sudden this bird landed on my pole! It stayed long enough for me to get a picture with my phone – see the lizard just on the other side of my noose? Well, just after I snapped the picture the bird spooked the lizard, and I didn’t see that particular sagrei again, but I think the picture is worth the missed catch. Any thoughts on the identity of the cheeky percher?

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Lizards on small islands bite harder than lizards on big islands… and why!

This Fall, one of my big data-driven dissertation chapters was published in Functional Ecology. The paper is called “Feed or Fight: Testing the impact of food availability and intraspecific aggression on the functional ecology of an island lizard.”

Long story short: we found that lizards on small islands were larger than lizards on big islands. Even more interesting though was that we found these small island lizards had proportionally stronger bites, that means, even controlling for the differences in body size, these lizards were biting especially hard. Now there are two big reasons we might expect lizards on small islands to have harder bites: one, hard bites enable them to eat more defended food, things like beetles and snails, that they wouldn’t have to eat on a big island with lots of juicy insects. Another explanation is that on small islands, lizards need a strong bite force to fight off other lizards and protect valuable resources – food, territories, or access to mates. Both stories make sense, but we set out to test which proved to be the stronger driver for P. erhardii in the Cyclades.

It turns out the answer is that bite force seems to be more related to the levels of lizard-on-lizard competition between islands. After flushing the stomachs of hundreds of lizards and painstakingly identifying all those little bug parts (see post here) the diets of the lizards weren’t all that different (at least in terms of hardness).

With the help of my brother, Ross, we’ve put together a video to talk about the paper. Give it a look here! He did a tremendous job of it! And (shameless plug) if you’re looking for a videographer for your own work, give him a call!

PIT Tagging Lizards

A critical component of this study is being able to keep track of who is who, every single year. There are a lot of tried and true methods for doing so, including the low-tech of removing the last joint of different combinations of toes. There’s the mid-tech: injecting multi-colored liquid plastic that congeals just under the skin to give a unique marker. Finally, the high-tech (and my favorite): PIT tags. PIT stands for “Passive Integrated Transponder” which means little tiny circuit that, when activated with an electrical current, replies with a unique identification code.

While toe clipping is a very common means of keeping track of individuals, it suffers from problems because lizards lose toes all the time in fights. To our knowledge though there are not yet PIT tag parlours on any of these islands (though I think the lizards think they’re really cool) so we can be very sure that we’re getting exactly the individuals we want.

The process of implanting a PIT tag is remarkably straight forward. Here’s a video:

As you can see, the PIT tag is tiny – it doesn’t seem to affect the lizard’s movement or behavior at all. Next year, we’ll be able to know exactly who is who!

Trap Collecting!

Hi Everyone,

Just a quick update to let you know I’m alive and well. Sorry for the long delay since last posting. I’ve quite literally been flat out every single day. Last week Tuesday thru Friday I was up and in the field at or before 6:00 am. I’m a herpetologist! We’re supposed to get up with the lizards at 10:30! There’s a reason I didn’t want to study birds.

Still, the early mornings have generated lots of adventures, which I fully intend to fill you in on asap. Until then though, here’s the product of my first early morning: the second set of sticky traps and pitfall traps I collected at the crack of dawn on Tuesday. All in all I had 144 sticky traps and 216 pitfall traps, which should hopefully give me a good snapshot of the insect communities around the rock walls.

After the craziness in Africa trying to smear tanglefoot on 3×5 index cards (read about it here) I decided to splurge and buy the real thing (for an additional $7) DEFINITELY a good investment. I also had the idea to preserve them in the plastic sheathes that fit into a 3 ring binder. Much better than my previous debacle with seran wrap in the field. So here they are… now all I have to do is sort through all of them, identify their order and count ’em up! Oh, and then sort through the soggy insects in the pitfall traps… I really need to do that soon…

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